1. Field of the Invention
The present invention relates to a thermal processing apparatus and a thermal processing method performing processing accompanied with heating on a substrate.
2. Description of the Background Art
A rapid thermal process (hereinafter abbreviated as “RTP”) plays an important role as one of heating steps for a semiconductor substrate (hereinafter referred to as “substrate”) as requirement for refinement of a device such as a semiconductor device is increased. In the RTP, an infrared lamp is mainly employed as a heating source for heating a substrate to a prescribed temperature of 1200° C., for example, at the level of seconds while keeping a prescribed gas atmosphere in a processing chamber and maintaining the substrate at the temperature for a constant time of several 10 seconds, for example, and the lamp is thereafter turned off for rapidly cooling the substrate.
The RTP is employed for performing processing, such as that for preventing an impurity from thermally re-diffusing in junction layers of transistors formed on a substrate or that for reducing the thickness of an insulator film such as an oxide film, for example, which has been hard to implement by prolonged thermal processing in a conventional electric furnace.
A generally known thermal processing apparatus performing the RTP is provided with two stages of parallelly arranged bar lamps. FIGS. 1 and 2 are longitudinal sectional views showing such a type of thermal processing apparatus 8. This thermal processing apparatus 8 has an upper lamp group 81, including bar lamps directed toward an X direction, arranged in a Y direction and a lower lamp group 82, including bar lamps directed toward the Y direction, arranged in the X direction.
A substrate 9 is horizontally arranged to be opposed to the lamp groups 81 and 82, and supported by an auxiliary ring 83 covering the periphery thereof. A window member 84 separating an internal space 80 into two portions is arranged between the lamp groups 81 and 82 and the substrate 9, while the upper surface of the upper lamp group 81 defines a reflector 80a for reflecting light emitted from the upper lamp group 81 and efficiently irradiating the substrate 9 with the light.
The auxiliary ring 83 is integrally heated with the substrate 9 thereby preventing heat dissipation from an end surface of the substrate 9 and maintaining temperature uniformity on the surface of the substrate 9. If the auxiliary ring 83 is insufficiently heated, the temperature on the peripheral edge of the substrate 9 is not increased either. In order to implement temperature uniformity of the substrate 9, therefore, it is important to sufficiently heat the auxiliary ring 83.
In the thermal processing apparatus 8 shown in FIG. 1, the reflector 80a can selectively irradiate a desired region of the substrate 9 with the reflected light from the upper lamp group 81, while no consideration is made as to light upwardly emitted from the lower lamp group 82. Therefore, it follows that the degree of contribution of the reflected light from the reflector 80a to heating of the auxiliary ring 83 is adjusted only through the upper lamp group 81.
In the thermal processing apparatus 8, further, a plurality of concave surfaces uniformly formed on the reflector 80a substantially homogeneously guide the reflected light from the upper lamp group 81 onto the substrate 9 and the auxiliary ring 83. In the case of such a reflector 80a, there is a possibility that the temperature of the auxiliary ring 83 cannot be sufficiently increased.
Thus, it can be said that the structure of the thermal processing apparatus 8 is unpreferable for sufficiently efficiently heating the auxiliary ring 83.